How accurate is Exbal for calculating velocity?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by JARHEAD1371, Sep 26, 2010.

  1. JARHEAD1371

    JARHEAD1371 Well-Known Member

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    I've worked up a load with 162 A-Max and 65.5 gr H1000 with my 7 SAUM. My zero is 300 yds and I shot the load at 600 yds yesterday and the estimated 2950 fps was way off. All impacts were at least 12" above my target. I adjusted the velocity to 3243 fps for this morning. I shot at 660 yds today and Exbal called for 7.5 MOA elevation. The group was still 4.5" high and Exbal calculated the velocity at 3371 fps. I'm finding to very hard to believe this calculation to be correct. I'm going to shoot at 900+ on the next good morning and see what my drop is using the 3371 calculation.

    Has anyone else had this "problem" with their load? Should I adjust the BC to match my drops or go with what Exbal calculates?
     

  2. Broz

    Broz Well-Known Member

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    I would guess that if you have corrected the program at 660 yards accuratly you will be on with it at 900. However I feel it is best to do your trajectory validation at the farthest disance you can as long as the conditions are good and the rifle will hold under 1 moa. The tighter it will group the better the drop data will be. The other thing to check is to make sure ou have input the correct BC for the bullet, proper scope height and varified when you crank your scope up it is giving you the proper elevation. For example shoot a shot at 100 yards then crank it up 20 moa and shoot again using the same point of aim. Your second shot should land 20.94 inches above the first shot.

    Also, this happened to me once, check to make sure your exbal program never got switched to meters. Some how once I accidently bumped and checked the meter box..:rolleyes:

    Jeff
     

  3. Broz

    Broz Well-Known Member

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    One more thing. Probably should recheck your zero too. If you are 1 moa high at your zero..3" at 300 yards, you will be 1 moa high everywhere like 6" at 600.

    I have found even when sooting through 2 chronys in line they both will lie to you. The proof is in the pudding.

    Jeff